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Colin A. Bretz, Gillian Treadwell, Katherine Hutchinson, John S. Penn; Calcium Signaling Inhibitors Reduce Retinal Cell Responses to High Glucose. Invest. Ophthalmol. Vis. Sci. 2011;52(14):3592.
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Hyperglycemia is recognized as a primary pathogenic factor in the development of diabetic complications. In the retina, increased blood glucose is thought to induce structural changes in capillaries, causing them to become functionally incompetent. We hypothesize that calcium signaling is responsible for modulating these effects of high glucose on retinal cells. The purpose of this study was to investigate the effects of calcium signaling inhibitors (FK-506 and Cyclosporin A) on induction of VEGF expression by high glucose in retinal cells known to play roles in retinal neovascularization secondary to diabetes.
Human Müller cells were isolated from donor tissue and cultured in either normal (5 mM) or high (25 mM) glucose medium with and without the IL-2 inhibitor FK-506 (100nM). 48 hours later, culture media were collected and analyzed for VEGF production by PCR and ELISA. Human retinal microvascular endothelial cells (HRMEC) were treated with normal or high glucose media with and without Cyclosporin A (CsA; 10 uM). Two hours later, the cells were stained for NF-AT to investigate its nuclear translocation as a potential mechanism tying calcium modulating enzymes to VEGF production.
Müller cells treated with high glucose medium demonstrated a two-fold increase in VEGF compared to cells treated with normal glucose medium (p value = .0098). This effect was 45% inhibited when the cells were treated with high glucose medium plus FK-506 (p value = .0153). NF-AT translocated from the cytosol to the nucleus in HRMEC treated with high glucose, and this effect was inhibited in cells treated with high glucose medium plus CsA.
We have demonstrated the effects of high glucose on two retinal cell types that are known to play roles in diabetic retinopathy. Furthermore, our findings demonstrate that these effects can be modulated with calcium signaling inhibitors (FK-506 and CsA). This suggests a mechanism of action for glucose induction of VEGF, and identifies a novel therapeutic target for the treatment of diabetic retinopathy.
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